Why SPF 100 Sunscreen Isn’t as Great as You Think It Is.

Why SPF 100 Sunscreen Isn’t as Great as You Think It Is.

Midsection Of Man Standing At Beach

The sun’s bright, and today’s adventure—whether it’s sitting at a game, sweating out a bike ride, or just hanging out at the beach—requires a sunscreen that’s not going to fail you. So you reach for the highest SPF (“sun protection factor”) number you can find. Because if slathering on a sunscreen that contains an SPF 50 allows you to stay out 50 times longer in the sun than you normally would without getting a sunburn, then wearing one that’s labeled SPF 100 is much more effective, right?

Theoretically, yes. But the real-world answer is that it’s a little more complicated. The Environmental Working Group points out that super-high SPFs don’t actually block out that many more skin-damaging rays. SPF 50 blocks out 98 percent of UVB rays, while SPF 100 blocks 99 percent.

So why is the FDA proposing, in pending regulations, to make the maximum SPF value on sunscreen labels SPF 60+? Part of it is that the high number makes you feel like you’re dramatically more protected, so you put it on before you go out and think it’s got you covered all day (it doesn’t). People rarely apply enough sunscreen to begin with, so already the number of blocked rays is lower. Then, if they don’t reapply it every two hours like you’re supposed to, they can get burned.

If you think you won’t be misled by SPF 100 claims, consider that the Environmental Working Group reports that a WHO researcher observed “profound changes in sun behavior” when people wore higher SPF sunscreens—people really wereless careful about sun exposure and reapplying when the numbers were higher. So there’s basis for the idea that SPF 100 sunscreens may actually be misleading in how well they protect you.

But are SPF 100 Sunscreens Effective?

A real-world study, published in the Journal of the American Academy of Dermatologyin 2018, had nearly 200 people applying SPF 50 on one side of their face and SPF 100 on the other. After a day in the sun, redness was showing in a little more than 40 percent of people on the side that was covered by SPF 50, while only 13 percent of the skin covered by SPF 100 was red.

Of course, that’s one study, on one day, so it doesn’t prove the case about whether SPF 100 sunscreens are significantly more effective than lower numbers when used as people really use them. But it does lead the Skin Cancer Foundation to agree that the issue is complicated, and to remind people to apply enough sunscreen to begin with to give it a chance to be effective, and then reapply it every two hours, and immediately after swimming or sweating.

But whether it’s 100, 60+, 50+, or anything else, SPF numbers aren’t the only keep-your-skin-safe issue. SPF only applies to the amount of UVB rays that are blocked. But UVA rays are damaging, too—they’re responsible for tanning as well as skin aging, and the shortest wavelengths of them can contribute to sunburn—and just looking at the SPF number doesn’t tell you whether a product protects you from UVA rays, too.

 Pick one, put it on, and enjoy your day in the sun.

Back to blog